Pulse starting circuit for electric discharge devices



March 1949. J. H. CAMPBELL 9 PULSE STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed Aug; 13, 1947 Inven 'mr: John H. Campbe LL,

Patented Mar. 22, 1949 PULSE STARTING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES John H. Campbell, Mentor Headlands, Ohio, assignor to General Electric Company, a corporation of New York Application August 13, 1947, Serial No. 768,328

Claims.

This invention relates to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to an improvement in the circuit and apparatus described in application Serial No. 528,535 of John Campbell, filed March 29, 1944, now Patent No.

2,456,859, and which is assigned to the assignee of this application.

Circuits now in Wide use with fluorescent lamps are provided with means for heating the filamentary electrodes and for impressing a high voltage of short duration across the electrodes for starting an electrical discharge therebetween. Some of these arrangements are provided to delay the application of the high voltage until the electrodes have reached the desired electron emitting temperature. In prior art arrangements the delay means or switch provided relatively slow starting occasioned by lingering preheating periods, and varying operating characteristics with age.

An object of my invention is to provide a new and improved circuit for starting and operating electric discharge devices employing filamentary electrodes.

Another object of my invention is to provide a. new and improved means for an electric discharge device which means function independently of the ballast employed.

A further object of my invention is to provide a new and improved means for impressing starting voltages across filamentary electrodes of an electric discharge device after an accurately determined period of electrode preheating which is reduced to a minimum or optimum value without sacrificing adequate preheating oi the electrodes.

A still further object of my invention is to provide an improved apparatus for the operation of an electric discharge device which apparatus involves a high degree of simplicity and which [can be produced at a relatively low cost.

Further features and advantages of my invention will appear from the following descripftion of species thereof.

For a better understanding of my invention reference may be had to the following description taken in connection with the accompanying operating circuit therefor incorporating my invention. Fig. 2 illustrates an embodiment of the starting apparatus illustrated in Fig. 1 incorporating certain aspects of my invention.

Referring to Fig. 1, I have there illustrated one embodiment of my invention as applied to an electric discharge device I. The electric discharge device I, such as a fluorescent lamp, therein illustrated comprises an elongated tubular or cylindrical envelope 2 having sealed into the ends thereof filamentary electrodes 3 and 4, each herein illustrated as comprising a coil, preferably in the form of a coiled coil of tungsten wire activated with oxides of alkalin earth metals such as a mixture of barium and strontium oxides. The envelope 2 contains a gaseous atmosphere such as a rare gas like neon, argon or mixtures thereof at a pressure of a few millimeters and a small quantity of mercury which, during the operation of the lamps, has a low pressure of the order of 10 microns. The device i may be a low pressure positive column lamp of the fluorescent type provided with a suitable phosphor or fluorescent coating. This fluorescent coating upon excitation by the radiation produced by an electric discharge between the electrodes, transforms a shorter wave radiation due to the discharge into longer wave radiation such as radiation within the visible range. For ease of starting a stripe or strip 5 of conductive material which, for example, may be a metallic paint or graphite mixed with potassium silicate, may be applied to the surface of device i. The starting strip 5 may be connected to one or both of the electrodes.

In accordance with my invention device I is connected across a suitable power supply circuit 6, 6' which for example may be a 115 volt, cycle alternating current source, or a volt direct current circuit, for supplying current to device i through a ballast 1 which, for example, may be 50 volt 0.6 ampere incandescent lamp. The ballast lamp 1 serves as a resistor which has a high positive temperature resistance coefficient and which operates on the steep part of its temperatureresistance curve. Although the discharge device has a negative impedance-current characteristic, the effect of the ballast predominates over that of the device; hence the circuit is stable. A convenient form of ballast resistor is a small tungsten filament incandescent lamp Whose rated voltage is appreciably higher than the small difference between the source voltage and the operating voltage of the device. The filament of the ballast lamp therefore operates at a temperature materially lower than that for which it is designed to operate as a light source, thus greatly increasing the life of the lamp '5. This ballast lamp, however, may serve a dual function, namely as a ballast for the electric discharge device and as an individual light source. A manual make and break control switch 8 may be used to connect device l to the power supply circuit.

The starting apparatus comprises an inductive device, or auto-transformer 9 responsive to the current conducted by device i and whose primary winding ii) is connected to the source 3, i and its secondary winding H is connected between filamentary electrode 3 and a point of device l intermediate its filamentary electrodes 3 and l. It is preferable that the end of the secondary winding connects with a metal clamp or other conductor shown. at 22 on or close to the wall of device 5, for example connected to the commonly employed reflector. An electrode preheating circuit l3, l3 shunts device I but includes the filamentary electrodes d and in series therewith. The electrode preheating circuit l3, it connected in shunt with device l, includes a magnetic vibratory switch i l, having an armature l5, and a pair of normally closed contacts lb and H. The magnetic field of the auto-transformer ii serves to actuate armature l5 and cause vibratory movement thereof upon energization of auto-transformer 9.

When the entire installation is energized by closing switch 8, current flows through the primary winding it of the auto-transformer 9, filamentary electrode 3, armature l5 and con tacts i6 and I! of magnetic vibratory switch id, filamentary electrode 4, and ballast l. The primary winding iii of auto-transformer ii actuates the armature i5 substantially instantaneously so that the normally closed contacts it and II open. At the instant contacts it and ii disengage each other, whether the source of current supply is direct or alternating, the combined effect of the voltage impulse impressed by the transformer and the heated condition of the electrodes causes the gas in the device to ionize whereupon the device starts. Having thus started the discharge current continues to flow through the primary winding id of the auto-transformer and the magnetic flux generated by this winding is adequate to retain the contacts in and H in the open position. If device I does not ignite at the first opening of the contacts I6 and I! of the repetitive magnetic switch Hi, current again flows through primary winding iii, elec-- trode 3, armature l5 and contacts I6 and I? of switch i, electrode i, and ballast l. Armature I5 is again actuated substantially instantaneously, contacts l6 and Il disengage each other, and a voltage impulse is again impressed across the electrode 3 and contact l2. Thus, the electromagnetic switch operates as a repetitive magnetic switch until the discharge device I ignites.

The ignition or starting devices and circuits may be adjusted to the discharge device l in such a manner that if the device 5 is faulty or non-operative the repetitive magnetic switch l3 will cease to operate after a predetermined number of starting attempts. This is commonly known as the lock-out arrangements in the prior art. Although the lock-out arrangement is not herein shown or described it may be applied to this circuit.

Fig. 2 illustrates an embodiment of my invention comprising an insulating base member l8, a core structure IS supported by member l8 and comprising horizontal magnetic members 2i? and 2| and a Vertical magnetic member 22, a vertical armature it supported by a non-magnetic structure 23 mounted on member l8 and supporting at one end thereof the movable contact l6, contact I1, and primary and secondary windings I0 and. I I wound about horizontal member 20. Contact I7 is mounted on a resilient arm 24 which afiords a counter-acting force to the movable contact It and causes contact ii to remain in engagement with contact 56 during part of its opening movement. A coil spring 25 holds contacts I6 and H in a normally closed position.

In accordance with my invention, I provide a starting and operating device and circuit which will after a predetermined interval of time after the initiation of current flow through the electrodes impress an operating voltage thereacross. Accordingly, I provide a repetitive magnetic switch of the vibratory type accurately controlled by an inductive element functioning independently of the ballast employed. Generally speaking, I provide an improved apparatus for the operation of an electric discharge device which apparatus involves a high degree of simplicity and which can be manufactured at a relatively low cost.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an electric discharge lamp having spaced electrodes at least one of which is of the filamentary type, means including a ballast impedance connected between said device and a source of current, inductive means comprising a primary winding means and secondary winding means, a vibratory magnetic switch having an armature responsive to the magnetization of said inductive means and normally closed contacts connected in series relation in a preheating circuit comprising said electrode of the filamentary type and said primary winding means, and said secondary winding means being connected to said discharge device to apply a starting voltage thereto.

2. In combination, an electric discharge de-- vice having spaced electrodes and an electrode preheating circuit connected in shunt therewith and including a magnetic vibratory starting switch having normally closed contacts, means includi a ballast impedance for connecting said device to a source of current, and a step-up transformer having its primary winding connected to be energized from said source in series relation with said contacts and its secondary winding connected to apply a starting voltage to said device, said switch being responsive :to the magnetization of said transformer.

3. In combination, an electric discharge device having spaced electrodes and an electrode preheating circuit connected in shunt therewith and including a switch having an armature and a pair of normally closed contacts, means including a ballast impedance connected between said device and a source of current, and a step-up transformer having its primary winding connected to said source and its secondary winding connected between one of said electrodes and a point of said device intermediate its electrode, the magnetic field of said transformer servin to actuate said armature and to cause vibratory movement of said armature upon energization of said transformer.

4. In combination, an electric discharge device having spaced electrodes and an electrode preheating circuit connected in shunt therewith and including a switch having an armature and a pair of normally closed contacts, means including a ballast impedance connected between said device and a source of current, and a step-up transformer having its primary winding connected to said source and its secondary windin connected to said discharge device to supply a starting voltage thereto, the magnetic field of said transformer serving to actuate said armature and to cause vibratory movement Of said armature upon energization of said transformer.

5. In combination, a source of current supply, a gaseous electric discharge device having spaced electrodes adapted to be initially heated to an electron emitting temperature, connections between one end of each of said electrodes and said source, a switch having an armature and a pair of normally closed contacts connecting th other ends of said electrodes, a voltage step-up autotransformer having its primary in one of said connections and having its secondary connected to a point on said discharge device intermediate said electrodes for application thereto of a starting voltage impulse, said armature being respon- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,010,879 Mutsaers Aug. 13, 1935 2,155,816 Babb Apr. 25, 1939 2,181,294 Biggs Nov. 28, 1939 2,272,770 Edwards Feb. 10, 1942 

